Rising crime statistics have enhanced the concern with building security and to the development of security devices and systems to protect life and property. A typical security system includes devices for monitoring the use of entrances to and within a building. Although monitoring devices may be prominently displayed to discourage casual intruders, it is preferable to conceal the devices to avoid alerting determined intruders who might then circumvent the devices.
One monitoring device known in the art utilizes a magnetically operated switch. The switch is mounted on a jamb above a door and a magnet is mounted on the upper edge of the door. The switch is either normally open or normally closed and assumes the opposite position in response to the magnet when it and the magnet are in closely spaced relation, as when the door is closed. The position of the switch is monitored, for example, by a light on a display panel connected in an electrical circuit with the switch.
With use of the arrangement described above, both the switch and the magnet are in a relatively conspicuous location and accessible to intruders; hence they may be readily disabled. Moreover, since both are additional attachments to the door and the jamb, extra installation time and mounting fixtures are required, increasing the cost of using the system.
Other monitoring devices incorporate a switch, such as a plunger or reed switch, on or in a hinge leaf, and the adjacent hinge leaf actuates the plunger or carries a permanent magnet. When the relative position of the leaves changes, the switch contacts operate to effect a desired circuit operation. U.S. Pat. Nos. 3,715,537, 3,806,852 and 3,896,404 are typical of prior art switch actuating hinges.